This invention relates to a magnetic particle powder included in magnetic toners used for magnetic image character recognition, which enables the formation of fine accurate images and the exact detection of encoded informations.
Researches on the complexing of different materials to provide a new composite material with high performance or novel functions have actively been pursued. Among them, a composite material comprising a magnetic particle powder and an organic polymer was already employed in magnetic printing materials and electrostatic latent image developers such as magnetic toners and carriers. In recent years, magnetic image character recognition, hereinafter referred to as MICR, is coming to be paid attention attractively, and developments and researches of the magnetic toners which can preferentially be used in MICR are also being carried out intensively. MICR is a technique wherein encoded informations can be read on the surface of a personal check or other document bearing images formed by ordinary characters and images formed and encoded by special numerals or characters to collect and identify such informations. It is particularly widely used for inspecting the personal checks in bank clearing houses. In conventional typography and planography, different inks had to be used for the ordinary character images and for the encoded images. Furthermore, as the ordinary characters and encoded characters could not be printed at the same time, serious problems arose in terms of workability and economic viability. To resolve these problems, a great need had arisen in recent years for magnetic toners that would enable the ordinary character images and the readable encoded images to be formed simultaneoulsy by laser beam printers which are now rapidly coming into wide use.
The magnetic toners used in MICR, as described hereinbefore, must therefore be capable not only of forming ordinary characters in the same way as toners used in the electrostatic image developers, but also of forming special numerals or images encoded by special characters in fine detail. Furthermore, it must also be possible to read the encoded images accurately.
It is particularly important to provide a better reliability when reading the encoded images. This requires a fine image quality with little background and as high an image density as possible. Also, the accurate reading of images requires that signal levels conform as far as possible to nominal signal levels. There was therefore a great need for improvements in the magnetic particle powders having a direct effect on the magnetic toners used to form the images so as to obtain toners with the desired properties.
Conventionally, the magnetic particle powders used in MICR magnetic toners were particulate magnetites such as acicular magnetite or "Mapico Black" supplied by Cities Services Co., as described in U.S. Pat. No. 4,517,268.
As present, there is a great need for new magnetic particle powders for the magnetic toners of MICR, which would enable the formation of fine accurate images and the exact detection of the encoded information. A toner fully satisfying these requirements however had not yet been produced using the conventional magnetic particle powders such as the conventional acicular magnetite or "Mapico Black".
The object addressed by this invention is thus to obtain a magnetic particle powder which is to be included in the magnetic toners used for MICR so as to enable the formation of fine accurate images and the exact detection of the encoded informations.